imo clayshale

Osadebe, C.C., Obrike, S. E. and Sulymon, N.A., 2011. Evaluation of Imo Clay-Shale Deposit (Paleocene) from

Okada, Edo State, Southwestern Nigeria, as Drilling Mud Clay.

Journal of Applied Technology in Environmental Sanitation, 1 (4): 311-316.

311

Original Report

EVALUATION OF IMO CLAY-SHALE DEPOSIT (PALEOCENE) FROM OKADA,

EDO STATE, SOUTHWESTERN NIGERIA, AS DRILLING MUD CLAY

OSADEBE, C.C.1, OBRIKE, S. E.2* and SULYMON, N.A.1

1Nigerian Building and Road Research Institute, P.M.B. 1055, Ota, Ogun State, Nigeria. 2Department of Geology and Mining, Nasarawa State University, Keffi, Nigeria. *Corresponding Author: Phone: +2348064306565; E-mail: [email protected]

Received: 16st July 2011; Revised: 24th August 2011; Accepted: 9th September 2011

Abstract: The dependence on the importation of drilling mud has much impact on the drilling operation in the country. Extensive field and laboratory investigation of Okada clay-shale revealed that the clay –shale deposit can be a good alternative to imported drilling mud when properly processed. X-ray diffraction studies carried out on the dis-turbed soil samples collected from the field showed the presence of vermiculite, montmo-rillonite and glauconite peaks, occurring as a mixed layer with traces of chlorite. District peaks of kaolinite, illite and quartz are also very visible. Chemical tests also showed that the SiO2 range from 55.75% to 55.84%, Al2O2 from 20.5% to 20.7%. The ratio of silica to alumina in both Okada shale and drilling mud are high, which is an indication of low quantity of free quartz. The average loss on ignition values for the Okada shale and drill-ing mud are 16.8 and 9.8 respectively. These values are high and indicate high water of crystallinity. The low content of K2O is an indication of the low amount of illite present. The mineralogical and chemical composition of both the Okada clay-shale and the im-ported drilling mud are such that Okada clay-shale can serve as a good alternative. However, the Okada clay-shale may require beneficiation, blending and refining pro-cesses to reduce its loss on ignition and SiO2 values. Keywords: Mineralogy, chemistry, clay-shale, drilling mud, evaluation

INTRODUCTION

Clays have over the years; serve as a very useful source of raw material for a wide range of industrial applications such as in the ceramics, pharmaceutical, agricultural and construction in-dustries. They have also been severally employed as drilling mud in drilling operation. As drilling fluid, they serve the dual function of increasing the viscosity of the drilling mud and sealing of the

This work is licensed under the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ISSN 2088-3218

Vo l ume 1 , Number 4 : 311 -316 , November , 2011 © T2011 Department of Environmental Engineer ing S e p u l u h N o p e m b e r I n s t i t u t e o f T e c h n o l o g y , S u r a b a y a & Indonesian Society of Sanitary and Environmental Engineers, Jakarta O p e n A c c e s s h t t p : / / w w w . t r i s a n i t a . o r g / j a t e s

I n t e r n a t i o n a l p e e r - r e v i e w e d j o u r n a l

International peer-reviewed journal




312

bore hole wall, so that the fluid being circulated are not lost to permeable formation being drilled [13].

Prevailing economic realities in developing countries with respect to increasing debt burden and low Gross Domestic Product (GDP), is gradually pushing towards reduction on import de-pendence and the encouragement of locally sourced raw materials. Bulk of the materials used for drilling operations in Nigeria are imported and huge amount of foreign exchange can be saved if some of these materials can be sourced locally. With a vast number of clay deposits nation-wide, that vary in composition from kaolin, vermiculite to montmorillonite [6], the compositional evalua-tion of these deposits as potential substitute for imported drilling mud clays will have immense positive influence on the economy.

MATERIALS AND METHODS

General description

The study area is located in Okada town, about 28km from Benin City, Edo State, south-western Nigeria. It falls within the geographical coordinates of latitude 6o 40/ - 60 45/ N and longi-tudes 50 20/ - 50 25/ E (Fig.1). The area is within the rain forest region of Nigeria with rainy season occurring from April to October. The mean annual rainfall values range from 1500mm to 1830mm [2]. Rainfall within the area are usually characterized by high surface runoff due to its generally low infiltration rates and high canopy trees [14].

Geologic setting

The clay-shale in Okada is part of Imo shale outcrop that is an arcuate belt from Western Ni-geria to the East. It lies conformably on the Maaestrichtian Abeokuta and Nsukka Formation [12]. The Imo Formation is essentially thick clayey shale, fine textured, dark grey to bluish grey with occasional admixture of clay ironstone and thin sandstone beds. The Imo shale range from Paleocene to lower Eocene in age [12]; [1] and [7]. The Formation is typically dark, very thinly laminated fissile and contains abundant pyrite crystals but poorly fossiliferous [11].

The Imo Formation in the eastern part is a lateral equivalent of the Akinbo Formation in Western Nigeria [8]. The Imo Formation outcrops at Okada as Okada shale. Okada clay-shale is therefore part of Imo Formation (Table 1).

Table1: Paleocene Stratigraphic sequence in Southern Nigeria (after [10])

Age Western Nigeria Eastern Nigeria

Eocene Paleocene Maestrichtian

Ameki Formation Ilaro Formation Oshosun Formation Akinbo Formation Ewekoro Formation Abeokuta Formation

Ameki Formation Lateral equivalent Nanka Sand Imo Formation Nsukka Formation

Twenty (20) disturbed and undisturbed soil samples were collected from the soil horizons of

the soil profile using hand auger and U-4 tubes in accordance with BS 1377 [4]. The samples were collected in polythene sample bags to prevent the loss of moisture. The soil samples were subjected to mineralogical and chemical analyses.




313

The mineralogical analysis was carried out using the X- ray diffraction method with the aid of Phillip machine, PW 1800. The soil samples were prepared using the cavity mount technique. The diffractometer chart of the soil samples from the X-ray diffractometer run were compared with well established standards and interpreted with reference to Brindley[3] and Brown [5] and Joint Committee on Powder Diffraction Standards [9] table of X-ray powder diffraction patterns.

The chemical analysis of the clay samples and drilling mud clay samples was conducted us-ing the Perkin Elmer Atomic Absorption Spectrophotometer (AAS ) for the determination of major Oxides ( SiO2, Al2O3, MgO, CaO, K2O, Na2O ) and trace elements ( Ni, Co, Cu, Cr. Pb, Mo ).

Fig. 1 Geological map Okada and adjoining areas.

RESULTS AND DISCUSSION

The diffractograms of the mineralogical analysis of the Okada clay-shale and drilling mud samples are presented in Fig 2 and 3. The diffractogram of the Okada clay-shale show that it consists mainly of vermiculite, montmorilonite and glauconite peaks, occurring as a mixed layer with traces of chlorite. Distinct peaks of kaolinite, illite and quartz are also very visible. The promi-nent basal reflection of the mixed layered minerals, illite and quartz as indicated by their strong and sharp peaks are indicative of moderate to well crystalline mineral component. The diffracto-gram of the drilling mud show that it is composed of mainly montmorillonite, kaolinite, illite, ver-miculite and quartz. The moderately sharp and prominent peaks exhibited are indicative of the degree of crystallinity.




314

Fig. 2 Typical diffractogram of the Okada shale sample

Fig. 3 Diffractogram of drilling mud sample.

The summary result of the chemical analysis of the Okada clay-shale and drilling mud are

presented in Table 2. The SiO2 values for Okada clay-shale range from 55.75% to 55.84% with an average value of 55.76% while the silica content of the drilling mud ranges from 57.60% to




315

57.9% with an average of 57.60%. The alumina values of Okada clay-shale range from 20.5% to 20.70% with an average value of 20.6%. The alumina content of drilling mud range from 27.30% to 27.7%. The ratio of silica to alumina in both Okada shale and drilling mud are high, which is an indication of low quantity of free quartz.

The average values of MgO, CaO, Na2O, and MnO for the Okada clay-shale are 0.20, 0.30, 2.0, and 0.02 respectively. However, the average composition of MgO, CaO, Na2O and MnO for the analyzed sample of drilling mud is 0.25, 0.20, 1.98 and 0.06 respectively. These values are low and have negligible effect on the shrinkage properties of the clays. The average loss on igni-tion values for the Okada clay-shale and drilling mud are 16.8 and 9.8 respectively. These values are high and indicate high water of crystallinty.

The predominance of SiO2 (55.75% – 55.84%), Al2O3 (20.5% - 20.70%) in the Okada clay-shale classifies it as hydrated alumino silicates. The MgO and CaO content are generally low in contrast to values for calcareous Ewekoro and Gombe shale [6]. The relatively high values of Na2O for both Okada clay-shale and drilling mud is most probably due to the significant propor-tion of montmorillonite and the low content of K2O, an indication of the low amount of illite pre-sent. The average loss on ignition values for the Okada clay-shale and drilling mud are 16.8 and 9.8 respectively. These values are high and indicate high water of crystallinity Very low mean val-ues of ferric oxide were recorded for both the Okada shale and drilling mud, suggesting the ab-sence of iron bearing minerals. Table 2: Average chemical composition of clay- shale in Okada and drilling mud

OKADA CLAY-SHALE DRILLING MUD Parameters (% Ox-ide)

Mean values Range Mean values Range

SiO2 55.77 55.71-55.84 57.60 57.3-57.90 Al2O3 20.6 20.58-20.70 27.50 27.3-27.70 Fe2O3 0.70 0.68-0.72 0.80 0.75-0.84 TiO2 1.15 0.8-1.92 1.26 1.24-1.28 MgO 0.2 0.16-0.22 0.25 0.23-0.28 CaO 0.3 0.28-0.32 0.20 0.2 Na2O 2.0 1.94-2.05 1.98 1.96-2.0 K2O 0.3 0.28-0.32 0.20 0.18-0.22 P2O5 0.012 0.01-0.02 0.06 0.04-0.08 MnO 0.02 0.01-0.04 0.06 0.06 LOI (Loss in igni-tion)

16.80 16.50-17.0 9.8 9.6-10.0

HEAVY METALS (mgL-1)

Mean values Range Mean values Range

Nickel 20.0 19.1-21.2 15.0 13.0-16.0 Cobalt 1.0 0.96-1.02 1.5 1.2-1.8 Copper 10.0 9.8-10.4 18 16.0-20.0 Chromium 30.0 29.8-32.0 15.0 13.0-16.5 Molybdenum 0.2 0.18-0.24 0.20 0.18-0.2 Lead 5.0 4.2-5.6 8.0 7.0-8.9




316

CONCLUSION The Imo clay-shale from Okada contains appreciable amount of vermiculite, chlorite, glauco-

nite and montmorillonite occurring as a mixed layer. It is essentially smectite dominated, with quartz as the main subsidiary non-clay mineral. The clay-shale is characterized by high loss on ignition which is an indication of high water of crystallinity. The result reveals that the Okada clay-shale and the drilling mud have close chemical composition. However, the Okada clay-shale may require beneficiation, blending and refining processes to reduce its loss on ignition and SiO2 val-ues. Consequently, the Okada clay-shale can serve as a good source of raw material for drilling. Private investors should be encouraged in the exploration and exploitation of the Okada clay- shale. Enormous savings on foreign exchange on importation of drilling mud will be saved and more job opportunities will be created with this new finding.

References 1. Adegoke, O.S., 1969.Eocene Stratigraphy of Southern Nigeria. Bull. Bur. Rech. Geol. Min. Mern. No.

69. Pp.23-48. 2. Akintola, J.O., 1986. Rainfall distribution in Nigeria. Impact Publishers Nigeria Limited, Ibadan, Nige-

ria 3. Brindley, G.W., 1980. Order-disorder in clay mineral structures. In Brindley G.W and G. Brown (eds)

Crystal Structure in clay minerals and their X-ray identification. Mineral Society, London 4. British Standard Institute, (B.S 1377) 1990. Method of Testing Soil Civil Engineering Purposes, Brit-

ish Standard, 1924 5. Brown, G., 1980. The X-ray identification and crystal structure of clay minerals. Min. Soc. London.

150 pp 6. Emofurieta, W.O., Ogundimu, F.O. and Imeokparia, E.G., 1994. Mineralogical Geochemical and

Economic Appraisal of some clay and shale deposits in South western and North Eastern Nigeria. Journal. Min. Geol. 30(2), 151-159.

7. Fayose, E.A., 1970. Stratigraphic Paleontology of Afowo 1 well, S.W Nigeria. Jour. Min.Geol. Nigeria. Vol.5, No1.

8. Fayose, E.A and Azeez, L.O., 1972. Micropaleontological investigation of Ewekoro area, S.W. Nige-ria. Micropal. Vol. 18, No.3, pp 369- 385

9. Joint Committee on Powder Diffraction Standards (JCPDS)., 1980. Selected powder difractttion data for minerals,Edition.(Ed. L.G.Berry). Pub. Joint Committee on Powder Diffraction Standards. Philadelphia. 813p

10. Kogbe, C.A. 1989. The Cretaceous and Paleogene Sediments of Southern Nigeria. In Kogbe, C.A. (ed), Geology of Nigeria

11. Ogbe, F.A.G., 1970. Stratigraphy of strata exposed in the Ewekoro Quarry Western. In Dessauvagie, T.F.J. and A.J. Whiteman (Eds) African Geology. Ibadan Univ. Press, Nigeria.

12. Reyment, R.A., 1965.Aspect of the Geology of Nigeria. Ibadan Univ. Press, 133p 13. Rogers, W.F., 1980. Composition and Properties of Oil Well Drilling Fluids, third edition. 14. Udoh, R.K., 1979. Geographical Regions of Nigeria, Ibadan, Heinemann

imo clayshale

Documents